Exactly, I think they caught on as they are a more intuitive UI than delving into your history or using bookmarks. When rendered repeatedly until you read them (perhaps weeks after,) they make for very expensive bookmarks.

Tabs/history/bookmarks I believe are the most pressing area for UI development in the browser.

A lot of this management could be pushed into the OS shell. If you could manage Windows easier - you wouldn't need tabs.

Tab behaviour is so inconsistent across browsers, apps and different OSs it hurts.